Starting anew in a new world is somewhat familiar to Jimmy, after all, he previously began anew from being a homeless person. But now, with more resources and stronger abilities, life is evidently going to be a little better.
From Jimmy's perspective, this ruin is an excellent location. The building carved inside the mountain is undoubtedly very sturdy. Unless there's substantial geological activity affecting the mountain, a minor earthquake at least won't compromise the main structure, at most just causing displacement of items.
On the first night after arriving, experiencing an earthquake did leave Jimmy somewhat shaken. He hadn't previously experienced disasters like earthquakes, volcanoes, or thunderstorms. Being taken away by such potential disasters in his sleep was too distressing, so his first thought was to find a safe place.
